1. Field of the Invention
The present invention relates to a power zoom lens, and a camera system having such a power zoom lens.
This application is related to the commonly assigned applications U.S. Ser. No. 07/410,880, U.S. Ser. No. 07/652,038, U.S. Ser. No. 07/407,424, U.S. Ser. No. 07/414,477, U.S. Ser. No. 07/414,478, U.S. Ser. No. 07/670,733, U.S. Ser. No. 07/406,523, and U.S. Ser. No. 07/414,476, the disclosures of which are expressly incorporated by reference herein.
2. Description of Related Art
There are various lens shutter type cameras having automatic focusing devices and power zoom lenses having zoom motors. In a known automatic focusing device in a single lens reflex camera, a focusing lens unit is moved by a motor in accordance with the detection results of a focus detecting device.
However, a power zoom single lens reflex camera having a power zoom lens has not been realized, since the provision of the power zoom lens not only complicates the mechanical construction of the camera body and electrical connection to the camera body, but also makes it difficult to realize a simple interchangeable mechanism which is capable of connecting both a power zoom lens and a conventional interchangeable lens to the camera body.
Furthermore, in a known single lens reflex camera, the driving operation of the motor is controlled by a microcomputer provided in the camera body. Since it is impossible to perform more than one complex operation at a time, the operations must be intermittently effected. An example of such a complicated operation which requires a relatively long time is automatic focus control. In an automatic focus control operation, an automatic focus adjusting process is first effected, and then, other necessary processes are carried out. Thereafter, the automatic focus adjusting process is again performed. Consequently, it takes a long time before all the necessary processes are completed. Accordingly, in a known single lens reflex camera, the operations which can be simultaneously effected are limited to a combination of one complex operation (i.e., time consuming operation) and one or more simple operations.
In addition to the foregoing, in a conventional single lens reflex camera, various operational switches are all provided on the camera body, rather than the taking lens. If the operational switches are provided on a taking lens, it is very difficult to detect the ON/OFF state of the switches. This results in a decreased operational efficiency.